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February 6, 2017

Study: Endoscopes can stay contaminated despite rigorous cleaning

Daily Briefing

Medical scopes could stay contaminated and might contain scratches or dents that could hold blood, tissue, and bacteria despite rigorous cleaning, according to a study published Tuesday in the American Journal of Infection Control, Chad Terhune reports for the Los Angeles Times.

Study details

For the study, researchers examined 20 endoscopes using a borescope, microbial cultures, and biochemical tests for protein and adenosine triphosphate. The scopes were divided into two groups:

  • One that followed current guidelines for cleaning processes; and
  • An intervention group that received more rigorous cleaning.

The researchers examined each scope three times over the seven-month study period to determine which scopes needed further cleaning or maintenance. The study focused on reusable colonoscopes and gastroscopes, which are widely used and believed to be easier to clean than more complex duodenoscopes.

All of the scopes—which were fairly new at the start of the study—were made by Olympus, which is under investigation for its production of medical endoscopes that have been linked to a series of superbug outbreaks.


Overall, the researchers found 12 of the 20 scopes tested positive for bacterial growth. The bacteria found on the scopes were not drug-resistant superbugs link to patient deaths, Terhune reports.

According to the study, 99 percent of the colonoscopes in both groups were deemed clean after the first cleaning. In comparison, just 48 percent of gastroscopes were deemed clean after the first cleaning, and 11 percent never met cleanliness standards, even after two manual cleanings and two rounds of automated cleaning and disinfection.

The researchers wrote that gastroscopes could become more resistant to cleaning because they are exposed to stomach acid and bile.

By the end of the study, 17 of the scopes were pulled from use and returned to Olympus for repair because of serious defects. According to the study, Olympus issued repair reports on 14 of the scopes and said 13 of them had at least one critical defect.


Study lead author Cori Ofstead, an epidemiologist in Minnesota, said, "Physicians, other caregivers, hospitals, and regulators should be paying keen attention to this issue, as patients have a right to assume that clean instruments are being used on them."

Olympus in a statement said it "welcomes additional research and perspectives as helpful to the entire medical community and our own efforts to increase patient safety related to endoscopes."

Separately, Michelle Alfa, a professor in the department of medical microbiology at the University of Manitoba and an adviser to U.S. regulators on scope testing, said, "Those scopes shouldn't be in use" (Terhune, Los Angeles Times, 1/31; Ofstead et al., American Journal of Clinical Infection Control, 2/1).

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